1. Field of the Invention
The present invention relates to an improved fish oil type composition having good preservative stability and heat resistance, which does not have a specific offensive fish oil odor after long term preservation and does not generate odor by heating. Further, the present invention relates to a preparation method for said fish oil type composition, an emulsion prepared using said composition and foods and cosmetics containing said composition or emulsion. The improved fish oil composition of this invention contains large amount of highly unsaturated fatty acid types such as DHA or EPA and ester thereof, and can be applied to foods, cosmetics and other uses because of said non odor feature of long term, good preservative stability and heat resistance.
2. Description of Prior Art
Specific kinds of highly unsaturated fatty acid and esters thereof contained in fish oil are known to be useful from the medical and dietetic view points. For example, since eicosapentaenoic acid (hereinafter, shortened to EPA) and its esters have effects to reduce the content of cholesterol in blood and to control thrombus, it is effective for the prevention and the medical treatment of cardiac infarction, cerebral infarction and arteriosclerosis. And docosahexaenoic acid (hereinafter, shortened to DHA) and its ester are known to have excellent effects for the improvement of learning function, antitumor effect, anti-allergy effect and improvement of eye sight. Further, both EPA and DHA have a good effect against atopic dermatitis. Therefore, highly unsaturated fatty acid and its ester are being developed to be applied to the use of foods, healthy foods, cosmetics and drugs, and several kinds of them are already developed and on the market as healthy foods and drugs.
However, the unsaturated bonds of highly unsaturated fatty acid and its ester can easily be decomposed and has a defect to generate specific offensive odor. To prevent this decomposition, the method to add an anti oxidation agent or a deodorant such as natural tocopherol, extract from tea and ascorbic acid are proposed, but these methods are not sufficient to obtain a good result. Further, the method to mix DHA with large amount of starch so as to wrap DHA in starch powder and to make it odorless is also provided. However, when the product obtained by said method is used, not only large amount of starch used for the wrapping of DHA gives bad effects to the taste of foods, but also the offensive odor based on DHA is not prevented, therefore, the possible amount of it to be used is restricted.
Concerning the above mentioned situation, the inventors of this invention have already found that the bread manufactured using starting material to which the suspension composed by DHA based fish oil and vinegar or citrus fruits juice does not generate offensive odor of fish oil and had already disclosed this art in Japanese Patent Laid open publication 7-274806 and Japanese Patent Laid open publication 7-270807. However, the suspension composed by DHA based fish oil (and vinegar or citrus fruits juice is odorless at the preparation of the suspension and can be effectively used at the production of bread. But, when the suspension is left for long term, the offensive odor is regenerated. That is, it is necessary to improve the preservative stability of it.
The inventors of this invention have conduced further intensive study to obtain a fish oil or a highly unsaturated fatty acid or an ester of it derived from fish oil which has good preservative stability and can maintain an odorless state effective for long term preservation. Consequently, the inventors of this invention have accomplished the following technique. That is, to fish oil or to a highly unsaturated fatty acid or an ester of it derived from fish oil, there is added at least one substance selected from the group composed by vinegar or citrus fruits juice and stirred, then the mixture (suspension) is settled so as to separate to oil phase and water phase. After removing of water phase, the oil phase is recovered as the modified fish oil. The obtained modified fish oil containing highly unsaturated fatty acid such as DHA or EPA and/or its ester, does not have an offensive odor in initial stage and does not generate offensive odor even after long term preservation.
The inventors of this invention have conducted further intensive study and have found that by the addition of vegetable oil to said modified fish oil type material, the initial odorless state can be maintained during long term preservation, namely becomes to have a good preservation stability and an offensive odor does not generate even if it is heated. Further the inventors have also found that the clearness of the modified fish oil can be further improved by adding at least one substance selected from the group composed by collagen, starch and agar--agar. At the preparation of foods and cosmetics containing fish oil or highly unsaturated fatty acid derived from the fish oil such as DHA or EPA and/or its ester, the possibility for the heat treatment during the preparation procedure is so many. Therefore, said excellent feature that the addition of vegetable oil to the modified fish oil prevents the generation of offensive odor and maintains an odorless state when it is heated, is very effective from the view point of the practical use of fish oil or highly unsaturated fatty acid derived from the fish oil and/or its ester.